Foil gauge



April 18, 1939.

c. M. HATHAWAY FOIL GAUGE Filed Feb. 19, 1957 Inventor Claude M. Hathaway,- bg xwyin lm Attorneg.

, 19 Ba ged.

i accommodating "terial varyin I Patented Apr l8, 1939 UNirsc STATES Y., assignor to General Electric Company, a corporation of New York Application m m c, 1931, Serial No. iz'aczi' '0 Claims. (01. 175- 183) My invention relates to electric gauges and concerns particularly thickness gauges for foil and metallic sheets. p V

I It is an object of my invention to provide a simple, sturdy, reliable, compact, and easily operated thickness gauge which is adapted to measure thickness of foil or sheets continuously, if d'esired, at any speed, and whichis unaflected by variations in position of the material being I It is a further object'of my invention to provide apparatus, which is adapted for gauging mawidely in thickness, in whichja gap may be employed for easily I the material to be gauged, and in which the measurement is relatively unaffected relatively large byvariations in the size of the gap for receiving the material being gauged.

till another obiectof my invention is to provide apparatus for automatically controlling the thickness offoil or sheet material during the Process of manufacture.

Additional objects of my invention arethe -measurement of thickness of metallic wire and y the measurement of conductivity or of purity of metallic sheets or wires of uniform thickness.

Other and further objects and advantages will become apparent as the description proceeds.

In carrying out my invention in-its preferred form, I provide a pair of jaws carrying co-operating parts of an electric gauge having agap through which the material to he smiled may be jg to the core. The

'by referring-to passed. The electric gauge includes a laminated m netic core with winding energized by'audio-frequency current and detecting'windings'which are responsive to the opposition presented to the passage of magwhen considered in connection with the accoml ying d'r'awing'and the features of my invention which are to be novel and'patentable will be in the claims appended hereto;

In the drawing llg. Iis aside view, partiallyin section, of one t of. my invention; Fig.

- 2is asectional viewcutby the plane 2-2 of Fig.

,jof Fig. 1 i is a'p spective view of one of- 1; rigtisthetopviewofthe apparatus of Figs.

l'and-fl'showing asection c'utbytheplanel- -i the core elements and the faceplateof the appa gratus of Figs. 1 to 3; Fig. 5 is sneleetric circuit diagram illustrating schematically the apparatus of l'igai to 4; and Pig. 6 is aperspective winding in inductive relation windings include an exciting the following detailed of the apparatus arranged for gauging wire. Like reference characters are utilized throughout the drawing to designate like parts.

Referring more in detail to the drawing, the

comprises a laminated field structure, windings carried thereon, a source of exciting current, and current-responsive apparatus for indicating gauge thickness or adjusting the sheet-manufacturing apparatus. The field structure includes an'H- shaped core element It with a pair'of parallel 1 881 and I! joined by a cross arm l8 and a pair of core elements l9 and 20. These core elements may be of U-shape' with parallel legs 2| and 22 and and 24, respectively. The legs 2i and 23 are in line with the legs ii of the H-shaped core element II. Likewise, the legs 22 and 24 are in line with the less H of the H-shaped core element ii. The U-shaped elements i9- and 2i! are spaced from the H-shaped element I i to form two pairs of air gaps 28 and 26 between confronting ends of the legs of the elementsof the'fleld structure.

The pair'of air gaps 26 is adapted to have the foil or other sheet material to be gauged pass through, and face plates 2! and 28. made of non-- conducting. nonmagnetic material are provided to cover the confronting ends of the core elements at the gap 28 for'protecting the moving foil against injury as well as providing a protective enclosure for the parts of the gauge head. The space betweenthe face plates 21 and 28 forms the gap l4 within which the sheet material 28 is caused to travel. It will be understoodthat the direction or travel of the's'heet'28 is perpendicular to the plane of the paperin the views of Figs-:1 and,

ii and parallel to the plane of the paper-in the I View of Fig. 2, the sheet, itself, being. perpendicuiar to the plane of the paper in elther'casei The H-shaped core element l5 carries an exciting winding on its connecting am It, and a sourceof alternating current is connected to theexciting winding 30 preferably through a rheo stat or variable impedance 32. The alternatingcurrent source 3| is-- preferably of audio fre-' quency: i. e below the radio frequency range; for example, it may be atwo thousand c'ycleper second source. For. relatively thick materials such as onesixteenth inch brass; :I' have'found drty cyclesto be satisfactory. "The; U-shaped core elements It and .20 carry the detecting 'windlugs 23 and "34,; respectively, and a current-re sponsive device, such as the rectifier-type alter hating-current mflliammeter 35, is connected to the windings 33 and 34, the connection being such that the windings '33 and 34 are in series-opposi- "relays -for operating a suitable thickness-controlling apparatus not shown. For example, a directional or polarized relay 33 may be connected in series with the instrument 31 and may be provided with oppositely placed contacts 33 and 43,

for energizingsuitable controls to increase or decrease the thickness of the sheet being produced. The apparatus for forming or rolling the sheets and the controls therefor do not form a part of my invention, and, consequently, are not illustrated in the drawing.

The apparatus may ,be arranged either as a null device or as a direct indicating device. In

either case, it is preferable to provide means for providing compensation under such conditions, a

balancing the fluxes produced when a sheet of some thickness, assumed as a standard thickness, is passed through the gap l4. For the purpose of sheet of material of standard thickness may be inserted in the pair of gaps 25 or a compensating winding 4| may be .wound upon a suitable part of the field structure, for example, upon the" U- Y shaped core element IS. The winding 4| is a closed circuit winding to simulate the eiIectof tained.

conducting material placed within the gap 25 and preferably the winding 4| is closed through an adjustable resistor or impedance 42 to permit adjustment of the amount of compensation ob- I have when gauging thin foil, it might be desirable to use a suppressed zero instrument as the instrument 31. For example, I may use a one milliampere instrument and suppress the zero by means of .the control springs' of the instrument so that one milliampere will be required to start the pointer moving away from zero and two milliamperes to give full scale deflection. Under these conditions, it might be expedient to .wind the compensating winding 4| on the U-shaped core element 20 instead of on the element l3. 3

In 'order to protect the partsof the electric auge l3 against dirt, against magnetic dust, and against particles of electrically-conducting material, the parts are preferably enclosed by cylindrical cases 43 and 44 closed at the ends by a plate 45 supporting the U-shaped core element Is, by the face plates 21 and 23, and by a base plate 46 resting upon the lower Jaw I2 and supporting the lower U -shaped cote element 20. The H-shaped core element 13 is supported by the face plate 21 secured to the cylindrical case 43 and the case 43 is in turn secured to the upper jaw l2.of the fixture II by a band 41.

The use. oi. audio-frequency as distinguished from high frequency current for energizing the apparatus results in magnetic flux capable of penetrating the toil 29 and'makes the readings relatively independent of the surface characteristics ofthe 011 and responsive only to its thickness. The useoi audio-frequency current also found that, in some cases, particularly makes it high-frequency generator and together with the use of iron core elements makes it possible to obtain sufiicient response for the operation of ordinary instruments and relays without the interP most cases of nonmagnetic metal, is passed from the rolls by which it is reduced to final size or to provide a vacuum-tube from a reel on which it may be stored through the gap 14 on to a reel upon whichit is rerolled. Since the sheet-23 is composed of electrically conducting material, it opposes the passage of flux across the pair of air gaps 23 and the strength of the opposition to flux depends upon transformer ratio'is varied by the opposition to flux passage produced bythe sheet 23. The detecting winding 33 also forms a second secondary winding of the transformer and, since the windings 33 and 34 are connected in.series-oppos ition,-j'

a variation in the opposition to flux produced by the sheet 29 varies the relative magnitudes of the voltages induced in the windings 33-and 34. The

rheostat 42 may accordingly be-adiusted to vary the eifect of the winding 4| and produce a null deflection oi the instrument when a sheet of the proper thickness is placed within the gap 14. H In case of deviations from the desired thickness, the opposition to flux crossing the pair of air gaps 26 will vary, varying the voltage induced in the windings 34 and'unbalancing the voltages appearing in thesecondary windings thereby producing a reading in the instrument 31, and 'operating the relay 33 in whichever direction is re-- quired. to correct the adjustment or the sheet--' producing apparatus. Ifdesired, of course, the rheostat 42 may be so set as to produce a zero deflection of the instrument 31 when no sheet is present in the gaps 23 and the instrument 31 may then be calibrated in terms ofthe thickness or" sheet passed through thegaps 23. In this case, a contact-making voltmeter will be substituted for the directional relay 33- andit willbe adjusted to operate at the voltage corresponding to the desired sheet thickness.

my apparatus in connection with thickness gaugingof sheets, it will be understood that my invenfor holding a wire 32 in the form of a loop with a portion 53 passing through the air gap l4 between the legs I 3 and 11 of the magnetic core element It. An additional rolleror sheave I4 is provided which is composed of material-which is nonmagnetic but which serves as a good conductor of electricity, such as copper-.- Consequently, an electrically-closed loop of wire is formed, notwithstanding the fact that the wire may travel -Although I have explained the operation of around the rollers continuously as the wire is passed through the testing apparatus. It will be understood that suitablearrangements are to be provided for keeping the wire 5: taut and maintaining a good contact at the roller l4. Obviously, the loop oi wire 52 reacts upon the magnetic field oi the apparatus and thus permits readings tobe obtained oi the thickness or purity oi the wire, as previously explained, as well as permitting indications of flaws, such as cracks or transverse cuts.

In accordance with the provisions oi the patent statutes, I have described the principle oi operation oi my invention, togetherwith the apparatus which I now consider to represent the best embodiment thereoi, but I desire to have it understood that the apparatus shown is only illustrative and that the invention-may becarried out by other means,

What I claim as new and desire to secure by v Letters Patent oi the United States is:

end of said H-shaped element to form air gaps between the ends of the parallel legs oi said latter U-shaped element and said H-shaped element, one oi said air gaps being adapted ior passage oi ioil to be gauged, a current-responsive device, detecting windings on each oi said U-' shaped elements connected to said currentresponsive device in series-opposition, a compensating winding on one 0! said U-shaped elements, and an adjustable resistor connected between the ends oi said compensating wind-- 2.,A ioil thickness gauge comprising in com- 7 bination, an H-sha'ped laminated core element with, parallel legs joined by a cross arm, an exciting winding on said cross arm, a source oi audio-frequency alternating current connected to said winding, a pair oi laminated core ole ments with end portions respectively adia'cent the ends-oi said H-shaped element to form air gaps between the ends oi the parallel legs oi said H-shaped element and saidother core elements, one oi said air gaps being adapted for passingioil'to be gauged, a current-responsive device, detecting windings linking said core elements on either side oi said cross arm and connected to said current-responsive device in branches, and a second detecting,

series-opposition, and compensating means in inductive relation to the portion oi the coreelements on the side of said cross arm opposite the air gap ior passing ioil to be gauged. 3. A ioil thickness gauge comprising in combination, a magnetic core elment with branches iorming parallel magnetic circuits, an exciting winding in inductive relation to both oi said magnetic core branches, a source oi audioirequency alternating current connected to said winding, each oi said magnetic core branches including a pair oi air gaps. one oi said pair oi air gaps being adapted ior passage oi ioil to be gauged, a current responsive device, a detecting winding linking once! said core winding link- 3 ing the other or said core branches. at least one oi said detecting windings being placed on the portion oi ,a branch oi the core separated y from the exciting winding by air gaps. said detecting windings being connected tosaid current responsive device in series opposition, and a closed current-conducting compensating circuit in inductive relation to one of said core branches at the portion thereoi separated irom said exciting windingby a pair of said air gaps.

4; A-icil thicknessgauge comprising in combination, a magnetic core element with branches iorming parallel magnetic circuits, an exciting winding in inductive relation to both oi said magnetic core branches, a; source oi .audiofrequency alternating current connected to said winding, each or said magnetic core branches including a pair of air gaps, one oi said air gaps being adapted for passage oi ioil to be gauged, a current responsive device, a detecting winding linking one of "said core branches, a second detecting winding linking the other of said core branches, and a current-conducting compensating circuit linking one of said core branches, each oi said detecting windings being placed on the portion of a branch oi the core separated from the exciting winding by a pair oi air gaps, said detecting windings being connected to said current responsivedevice in series opposition and said compensating circuit having a portion thereoi on the same portion oi a core branch as one of said detecting windings.

5. A continuous gauge for electrically conducting material comprising in combination, a mag-,

netic core element with branches iorming pare allel magnetic circuits, an exciting windingin inductive relation to both of said magnetic core branches, a source of audio-frequency alternating current 'connectedzto said winding, means ior passing electrically conducting material iorming a closed eddy current path in inductive relation to one of said core branches, a current responsive device, a detecting winding linking one oi said core branches, and a second detecting winding linking the other oi said core branches, said detecting windings being connected to said current responsive device in series opposition, and compensating means in inductive relation to one oi said core branches.

A continuous gauge for electrically conduct- .ing material comprising in combination, a magnetic core element with branches iorming parallel magnetic circuits, an exciting winding in inductiverelation to both oi said magnetic core branches, a source oi audio-irequency alternating current connected to said winding, one oi 'said magnetic core branches including a pair oi air gaps, one oi said magnetic core branches material to be gauged in inductive relation to said core branch, a current responsive device, a detecting winding linking one oi said core branches, a second detectingwinding linking the other oi said core branches. at least one oi said detecting windings being placed on the portion,

oi its branch oi the core separated irom the being adapted to receive electrically conducting excltingwhzdlng by said air gaps, said detecting windings being connected to said current responsive device in series opposition, and compe'nsating means in inductive relation to-one oi said core branches.

omens a. ns'rnswsr. 

